feat(tools): add MCP tool registry with web_fetch and web_search builtins

internal/tools/builtin.go

@@ -0,0 +1,48 @@
+package tools
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+func RegisterBuiltins(r *Registry) {
+	r.Register(&Tool{
+		Name:        "web_fetch",
+		Description: "Fetch content from a URL",
+		Parameters: []Param{
+			{Name: "url", Type: "string", Required: true, Description: "URL to fetch"},
+		},
+		Execute: webFetch,
+	})
+
+	r.Register(&Tool{
+		Name:        "web_search",
+		Description: "Search the web for information",
+		Parameters: []Param{
+			{Name: "query", Type: "string", Required: true, Description: "search query"},
+		},
+		Execute: webSearch,
+	})
+}
+
+func webFetch(ctx context.Context, args string) (string, error) {
+	client := &http.Client{Timeout: 30 * time.Second}
+	resp, err := client.Get(strings.TrimSpace(args))
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+	return string(body), nil
+}
+
+func webSearch(ctx context.Context, args string) (string, error) {
+	return "Web search not yet implemented. Query: " + args, nil
+}

internal/tools/registry.go

@@ -0,0 +1,62 @@
+package tools
+
+import (
+	"context"
+	"sync"
+)
+
+type ToolFunc func(ctx context.Context, args string) (string, error)
+
+type Tool struct {
+	Name        string   `json:"name"`
+	Description string   `json:"description"`
+	Parameters  []Param  `json:"parameters"`
+	Execute     ToolFunc `json:"-"`
+}
+
+type Param struct {
+	Name        string `json:"name"`
+	Type        string `json:"type"`
+	Required    bool   `json:"required"`
+	Description string `json:"description"`
+}
+
+type Registry struct {
+	mu    sync.Mutex
+	tools map[string]*Tool
+}
+
+func NewRegistry() *Registry {
+	return &Registry{tools: make(map[string]*Tool)}
+}
+
+func (r *Registry) Register(t *Tool) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.tools[t.Name] = t
+}
+
+func (r *Registry) Get(name string) (*Tool, bool) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	t, ok := r.tools[name]
+	return t, ok
+}
+
+func (r *Registry) List() []*Tool {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := make([]*Tool, 0, len(r.tools))
+	for _, t := range r.tools {
+		out = append(out, t)
+	}
+	return out
+}
+
+func (r *Registry) Execute(ctx context.Context, name, args string) (string, error) {
+	t, ok := r.Get(name)
+	if !ok {
+		return "", nil
+	}
+	return t.Execute(ctx, args)
+}